As a result of recent regulatory initiatives, motor vehicle emissions aftertreatment devices are required to have longer useful lives. For example, in the 1990's, the United States Environmental Protection Agency (EPA) increased the mileage for which automotive emission control elements must function from 50,000 to 100,000 vehicle miles. This requirement places severe demands on emissions control devices as they age. As one example of the deleterious effects of aging, various exhaust gas components can “poison” a catalytic type emissions treatment device over time.
To understand the effects of aging of emissions control devices, it is necessary to have a test system and procedure that will permit the evaluation of the long term effects of individual variables that may affect the performance of the device.
Historically, “engine-based” test systems, which receive emissions from actual internal combustion engines have been used for such evaluations. However, engine-based systems can be inconsistent, maintenance intensive, and expensive to operate. In addition, engine-based systems do not conveniently permit the separate evaluation of individual variables, such as the effects of fuel and oil constituents. Also, in engine-based systems, engine oil consumption varies with engine age, operating temperature, speed and other variables, which are all difficult to control.